KR102211367B1 - Organic electrolyte and lithium battery employing said electrolyte - Google Patents

Abstract

Organic solvent; Lithium salt; A borate compound represented by Formula 1; And an organic electrolyte containing the ionic metal complex compound represented by Chemical Formula 2, and a lithium battery containing the organic electrolyte.

Description

An organic electrolyte and a lithium battery employing the electrolyte {ORGANIC ELECTROLYTE AND LITHIUM BATTERY EMPLOYING SAID ELECTROLYTE}

It relates to an organic electrolyte and a lithium battery employing the electrolyte.

Lithium batteries are used as power sources for portable electronic devices such as video cameras, mobile phones, and notebook computers. The rechargeable lithium secondary battery has more than three times the energy density per unit weight and can be charged at a high speed compared to conventional lead storage batteries, nickel-cadmium batteries, nickel hydrogen batteries, and nickel zinc batteries.

Since the lithium battery operates at a high driving voltage, an aqueous electrolyte having high reactivity with lithium cannot be used. In general, an organic electrolyte is used for lithium batteries. The organic electrolyte is prepared by dissolving a lithium salt in an organic solvent. The organic solvent is preferably stable at high voltage, high ionic conductivity and dielectric constant, and low viscosity.

When a carbonate-based polar non-aqueous solvent is used in a lithium battery, an irreversible reaction occurs in which an excessive amount of charge is used due to a side reaction between the cathode/anode and the electrolyte during initial charging. By the irreversible reaction, a passivation layer such as a solid electrolyte interface (SEI) is formed on the surface of the cathode.

The lithium salt reacts with the organic solvent of the electrolyte during the charging and discharging process to consume the organic solvent, generate gas, and form a solid electrolyte film having high resistance, resulting in deterioration of the life characteristics of the lithium battery.

Accordingly, there is a need for an organic electrolyte solution capable of suppressing gas generation and preventing deterioration of life characteristics of a lithium battery by forming a solid electrolyte film having low resistance.

One aspect is to provide a new organic electrolyte.

Another aspect is to provide a lithium battery including the organic electrolyte.

According to one aspect,

Organic solvent;

Lithium salt;

A borate compound represented by the following formula (1); And

An organic electrolyte containing an ionic metal complex represented by the following formula (2) is provided:

<Formula 1> <Formula 2>

In the above equations,

R ₁ , R ₂ and R ₃ are each independently hydrogen; A halogen substituted or unsubstituted C1 to C5 alkyl group; Or a halogen substituted or unsubstituted C 1 to C 5 cyanoalkyl group; And,

At least one of R ₁ , R ₂ and R ₃ includes a cyanoalkyl group,

Me is an element selected from the group consisting of transition metals and elements belonging to groups 13 to 15 of the periodic table,

M is a metal ion,

a is an integer of 1 to 3, b is an integer of 1 to 3, s=b/a,

p is 0 to 8, q is 0 or 1, r is 1 to 4,

X ₁ and X ₂ are each independently O, S, or NR ₆ ,

R ₄ and R ₆ are each independently a halogen, a halogen substituted or unsubstituted C 1 to C 5 alkyl group, or a halogen substituted or unsubstituted C 1 to C 5 aryl group,

R ₅ is an alkylene group having 1 to 5 carbon atoms substituted or unsubstituted with halogen, or an arylene group having 4 to 10 carbon atoms substituted or unsubstituted with halogen.

According to another aspect,

anode;

cathode; And

A lithium battery comprising the organic electrolyte according to the above is provided.

According to one aspect, the life characteristics of a lithium battery can be improved by using an organic electrolyte of a new composition.

1A is a graph showing the life characteristics of lithium batteries manufactured in Examples 1 to 2 and Comparative Examples 1 to 6 at room temperature (25°C).
1B is a graph showing the life characteristics of lithium batteries manufactured in Examples 7 to 8 and Comparative Examples 1 and 7 at room temperature (25°C).
1C is a graph showing high temperature (45°C) life characteristics of lithium batteries prepared in Examples 7 to 8 and Comparative Examples 1 and 7.
2 is a schematic diagram of a lithium battery according to an exemplary embodiment.
<Explanation of symbols for major parts of drawings>
1: lithium battery 2: negative electrode
3: anode 4: separator
5: battery case 6: cap assembly

Best mode for carrying out the invention

Hereinafter, an organic electrolyte according to exemplary embodiments and a lithium battery employing the organic electrolyte will be described in more detail.

The organic electrolyte according to an embodiment is an organic solvent; Lithium salt; A borate compound represented by the following formula (1); And an ionic metal complex represented by the following formula (2):

<Formula 1> <Formula 2>

In the above equations,

R ₁ , R ₂ and R ₃ are each independently hydrogen; A halogen substituted or unsubstituted C1 to C5 alkyl group; Or a halogen-substituted or unsubstituted C1 to C5 cyanoalkyl group; wherein at least one of R ₁ , R ₂ and R ₃ contains a cyanoalkyl group, and Me is a transition metal and Group 13 of the Periodic Table of the Elements To an element selected from the group consisting of elements belonging to Group 15, M is a metal ion, a is an integer of 1 to 3, b is an integer of 1 to 3, s=b/a, and p is 0 to 8, q is 0 or 1, r is 1 to 4, X ₁ and X ₂ are each independently O, S, or NR ₆ , and R ₄ and R ₆ are each independently substituted with halogen or halogen, or Unsubstituted C 1 to C 5 alkyl group, or a halogen substituted or unsubstituted C 1 to C 5 aryl group, and R ₅ is a halogen substituted or unsubstituted C 1 to C 5 alkylene group, or halogen substituted or It is an unsubstituted C4-10 arylene group. For example, M may be an alkali metal ion or an alkaline earth metal ion.

The organic electrolyte suppresses generation of gas and suppresses formation of a solid electrolyte film having high resistance, thereby preventing deterioration in battery performance such as life characteristics of a lithium battery.

The reason why the organic electrolyte improves the performance of the lithium battery will be described in more detail below, but this is to aid understanding of the present invention, and the scope of the present invention is not limited to the scope of the description below.

For example, since the borate compound can accommodate anions, it is possible to improve the ionic conductivity of the organic electrolyte by promoting dissociation of the lithium salt. In addition, the ionic metal complex of Formula 2 may have a chemically stable structure by bonding while forming a ring with heteroatoms X ₁ and X ₂ to the central atom Me. Accordingly, the organic electrolyte solution containing the ionic metal complex compound may have improved heat resistance, chemical stability, and hydrolysis resistance in addition to improved ionic conductivity.

Accordingly, since the organic electrolyte contains a borate compound and an ionic compound at the same time, high ionic conductivity, improved heat resistance, and hydrolysis resistance can be simultaneously provided. As a result, the stability of the lithium battery including the organic electrolyte may be improved and life characteristics may be improved.

For example, the borate compound in the organic electrolyte may be represented by the following formula (3):

<Formula 3>

B(OR ₁₀ ) ₃

In the above formula, R ₁₀ is cyanoalkyl having 1 to 5 carbon atoms unsubstituted or substituted with halogen.

For example, the borate compound in the organic electrolyte may be tricyanomethylborate, tricyanoethylborate (tris(2-cyanoethyl)borate), tricyanopropylborate, or tricyanobutylborate, but is not limited thereto. It is a borate compound corresponding to Lewis acid, and any compound having anionic capacity is possible.

For example, the ionic metal complex compound in the organic electrolyte may be represented by Formula 4:

<Formula 4>

In the above formula, Ma is Al, B or P, M is a metal ion, p is 0 to 8, q is 0 or 1, r is 1 to 4, X ₃ and X ₄ are each independently O or S, R ₇ is halogen, R ₈ is independently a halogen-substituted or unsubstituted C 1 to C 5 alkylene group, or a halogen-substituted or unsubstituted C 4 to C 10 arylene group.

For example, the ionic metal complex compound in the organic electrolyte may be represented by Formula 5 or 6:

<Formula 5> <Formula 6>

In the above formulas, Ma is Al, B or P, p is 0 to 8, r is 1 to 4, R ₇ is halogen, R ₉ is an alkylene group having 1 to 5 carbon atoms substituted or unsubstituted with halogen to be.

Specifically, the ionic metal complex compound in the organic electrolyte may be represented by Formulas 7 to 12 below.

<Formula 7> <Formula 8>

<Formula 9> <Formula 10>

<Formula 11> <Formula 12>

.

.

The content of the borate compound in the organic electrolyte may be 0.1 to 10% by weight based on the total weight of the organic electrolyte, but is not necessarily limited to this range, and an appropriate amount may be used as needed. For example, the content of the borate compound in the organic electrolyte may be 0.1 to 7% by weight based on the total weight of the organic electrolyte. For example, the content of the borate compound in the organic electrolyte may be 0.1 to 5% by weight based on the total weight of the organic electrolyte. For example, the content of the borate compound in the organic electrolyte may be 0.1 to 3% by weight based on the total weight of the organic electrolyte. Further improved battery characteristics may be obtained within the above content range.

The content of the ionic metal complex in the organic electrolyte may be 0.1 to 10% by weight based on the total weight of the organic electrolyte, but is not necessarily limited to this range, and an appropriate amount may be used as needed. For example, the content of the ionic metal complex compound in the organic electrolyte may be 0.1 to 7% by weight based on the total weight of the organic electrolyte. For example, the content of the ionic metal complex compound in the organic electrolyte may be 0.1 to 5% by weight based on the total weight of the organic electrolyte. For example, the content of the ionic metal complex compound in the organic electrolyte may be 0.1 to 3% by weight based on the total weight of the organic electrolyte. Further improved battery characteristics may be obtained within the above content range.

The organic electrolyte may additionally contain a fluorine-based compound represented by the following formula (13):

<Formula 13>

In the above formula, X ₁ and X ₂ are each independently hydrogen; halogen; It is an alkyl group unsubstituted or substituted with a halogen having 1 to 2 carbon atoms, and at least one of X ₁ and X ₂ contains a fluorine atom.

By additionally including the fluorine-based compound, the viscosity of the organic electrolyte may be reduced. As the viscosity of the organic electrolyte decreases, impregnation properties of the organic electrolyte may be improved and ionic conductivity may be improved.

The fluorine-based compound in the organic electrolyte may be represented by the following formulas 14 to 15:

<Formula 14> <Formula 15>

.

.

The content of the fluorine-based compound in the organic electrolyte may be 0.1 to 10% by weight based on the total weight of the organic electrolyte, but is not necessarily limited to this range, and an appropriate amount may be used as needed. For example, the content of the fluorine-based compound in the organic electrolyte may be 0.1 to 7% by weight based on the total weight of the organic electrolyte. For example, the content of the fluorine-based compound in the organic electrolyte may be 0.1 to 5% by weight based on the total weight of the organic electrolyte. For example, the content of the fluorine-based compound in the organic electrolyte may be 0.1 to 3% by weight based on the total weight of the organic electrolyte. Further improved battery characteristics may be obtained within the above content range.

The composition ratio of the borate compound, the ionic metal complex and the fluorine-based compound in the organic electrolyte may be 20 to 500 parts by weight of the ionic metal complex and 20 to 500 parts by weight of the fluorine-based compound, but is not necessarily limited to this range. And may be appropriately selected within a range that does not impair the effects of the present invention. For example, the composition ratio of the borate compound, the ionic metal complex and the fluorine-based compound in the organic electrolyte may be 20 to 400 parts by weight of the ionic metal complex and 20 to 400 parts by weight of the fluorine-based compound based on 100 parts by weight of the borate compound. For example, the composition ratio of the borate compound, the ionic metal complex and the fluorine-based compound in the organic electrolyte may be 20 to 300 parts by weight of the ionic metal complex and 20 to 300 parts by weight of the fluorine-based compound based on 100 parts by weight of the borate compound.

The organic solvent in the organic electrolyte may include a low boiling point solvent. The low boiling point solvent refers to a solvent having a boiling point of 200°C or less at 25°C and 1 atmosphere.

For example, the organic solvent includes at least one selected from the group consisting of dialkyl carbonates, cyclic carbonates, linear or cyclic esters, linear or cyclic amides, aliphatic nitriles, linear or cyclic ethers, and derivatives thereof. can do.

More specifically, the organic solvent is dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, diethyl carbonate (DEC), dipropyl carbonate, propylene carbonate (PC), ethylene carbonate (EC ), butylene carbonate, ethyl propionate, ethyl butyrate, acetonitrile, succinonitrile (SN), dimethylsulfoxide, dimethylformamide, dimethylacetamide, gamma-valerolactone, gamma-butyrolactone, and tetrahydro It may include one or more selected from the group consisting of furan, but is not necessarily limited thereto, and any low boiling point solvent that can be used in the art may be used.

The concentration of the lithium salt in the organic electrolyte may be 0.01 to 2.0 M, but is not necessarily limited to this range, and an appropriate concentration may be used if necessary. Further improved battery characteristics may be obtained within the above concentration range.

The lithium salt used for the organic electrolyte is not particularly limited, and any lithium salt that can be used in the art may be used. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ ) (C _y F _2y+1 SO ₂ ) (x, y are 1 to 20), LiCl, LiI, or a mixture thereof, and the like may be used. For example, in the organic electrolyte, the lithium salt may be LiPF ₆ .

The organic electrolyte may be in a liquid or gel state. The organic electrolyte may be prepared by adding the above-described borate compound, ionic metal complex compound, and lithium salt to an organic solvent.

A lithium battery according to another embodiment includes a positive electrode; It includes a negative electrode and the organic electrolyte according to the above. The shape of the lithium battery is not particularly limited, and includes lithium secondary batteries such as lithium ion batteries, lithium ion polymer batteries, and lithium sulfur batteries, as well as lithium primary batteries.

For example, in the lithium battery, the positive electrode may include nickel. For example, the positive electrode active material of the positive electrode may be a lithium transition metal oxide containing nickel. For example, the positive electrode active material of the positive electrode may be a nickel-rich lithium transition metal oxide having the largest amount of nickel among transition metals.

For example, in the lithium battery, the negative electrode may include graphite as a negative electrode active material. In addition, the lithium battery may have a high voltage of 4.8V or higher.

For example, the lithium battery may be manufactured by the following method.

First, the anode is prepared.

For example, a positive electrode active material composition in which a positive electrode active material, a conductive material, a binder, and a solvent are mixed is prepared. The positive electrode active material composition is directly coated on a metal current collector to prepare a positive electrode plate. Alternatively, the positive electrode active material composition may be cast on a separate support, and then a film peeled from the support may be laminated on a metal current collector to prepare a positive electrode plate. The anode is not limited to the shapes listed above, but may be in a shape other than the above shape.

The positive electrode active material is a lithium-containing metal oxide and may be used without limitation as long as it is commonly used in the art. For example, one or more of a complex oxide of a metal and lithium selected from cobalt, manganese, nickel, and combinations thereof may be used, and a specific example thereof is Li _a A _1-b B _b D ₂ (the Where 0.90≦a≦1.8, and 0≦b≦0.5); Li _a E _1-b B _b O _2-c D _c (where 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05); LiE _2-b B _b O _4-c D _c (where 0≦b≦0.5, 0≦c≦0.05); Li _a Ni _1-bc Co _b B _c D _α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α ≤ 2); Li _a Ni _1-bc Co _b B _c O _2-α F _α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Co _b B _c O _2-α F ₂ (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b B _c D _α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α ≤ 2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0.001≦d≦0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0.001≦e≦0.1); Li _a NiG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a CoG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a MnG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90≦a≦1.8 and 0.001≦b≦0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0≦f≦2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0≦f≦2); A compound represented by any one of the formulas of LiFePO ₄ can be used:

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or combinations thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

For example, LiCoO ₂ , LiMn _x O _2x (x=1, 2), LiNi _1-x Mn _x O _2x (0<x<1), LiNi _1-xy Co _x Mn _y O ₂ (0≤x≤ 0.5, 0≤y≤0.5, 1-xy>0.5), LiFePO ₄ and the like.

Of course, one having a coating layer on the surface of the compound may be used, or a mixture of the compound and a compound having a coating layer may be used. The coating layer may contain a coating element compound of oxide, hydroxide, oxyhydroxide of coating element, oxycarbonate of coating element, or hydroxycarbonate of coating element. The compound constituting these coating layers may be amorphous or crystalline. As a coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used. The coating layer formation process may be any coating method as long as the compound can be coated by a method that does not adversely affect the physical properties of the positive electrode active material by using these elements (e.g. spray coating, dipping method, etc.). Since the content can be well understood by those engaged in the relevant field, detailed description will be omitted.

Carbon black, graphite fine particles, etc. may be used as the conductive material, but are not limited thereto, and any material that can be used as a conductive material in the art may be used.

As the binder, vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene and mixtures thereof, or styrene butadiene rubber-based polymer, etc. Although may be used, it is not limited thereto, and any one that can be used as a binder in the art may be used.

As the solvent, N-methylpyrrolidone, acetone, water, and the like may be used, but are not limited thereto, and any solvent that can be used in the art may be used.

The contents of the positive electrode active material, the conductive material, the binder, and the solvent are generally used in lithium batteries. One or more of the conductive material, the binder, and the solvent may be omitted depending on the use and configuration of the lithium battery.

Next, the cathode is prepared.

For example, an anode active material composition is prepared by mixing an anode active material, a conductive material, a binder, and a solvent. The negative electrode active material composition is directly coated and dried on a metal current collector to prepare a negative electrode plate. Alternatively, after the negative active material composition is cast on a separate support, a film peeled from the support may be laminated on a metal current collector to prepare a negative electrode plate.

The anode active material may be any material that can be used as an anode active material for lithium batteries in the art. For example, it may include at least one selected from the group consisting of lithium metal, a metal alloyable with lithium, a transition metal oxide, a non-transition metal oxide, and a carbon-based material.

For example, the metal alloyable with lithium is Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloy (wherein Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth Element or a combination element thereof, not Si), Sn-Y alloy (the Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or a combination element thereof, not Sn ), etc. The element Y is Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, It may be Se, Te, Po, or a combination thereof.

For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, or the like.

For example, the non-transition metal oxide may be SnO ₂ , SiO _x (0<x<2), or the like.

The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as amorphous, plate-shaped, flake, spherical or fibrous natural graphite or artificial graphite, and the amorphous carbon is soft carbon (low temperature calcined carbon) or hard carbon (hard carbon). carbon), mesophase pitch carbide, calcined coke, or the like.

In the negative electrode active material composition, the conductive material and the binder may be the same as those of the positive electrode active material composition.

The contents of the negative electrode active material, the conductive material, the binder, and the solvent are generally used in lithium batteries. One or more of the conductive material, the binder, and the solvent may be omitted depending on the use and configuration of the lithium battery.

Next, a separator to be inserted between the positive and negative electrodes is prepared.

Any of the separators can be used as long as they are commonly used in lithium batteries. Those having low resistance to ion migration of the electrolyte and excellent in the ability to impregnate the electrolyte may be used. For example, as selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, it may be a non-woven fabric or a woven fabric. For example, a rollable separator such as polyethylene or polypropylene may be used for a lithium ion battery, and a separator having excellent organic electrolyte impregnation ability may be used for a lithium ion polymer battery. For example, the separator may be manufactured according to the following method.

A polymer resin, a filler, and a solvent are mixed to prepare a separator composition. The separator composition may be directly coated and dried on an electrode to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled off from the support may be laminated on an electrode to form a separator.

The polymer resin used for manufacturing the separator is not particularly limited, and all materials used for the bonding material of the electrode plate may be used. For example, vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof may be used.

Next, the organic electrolyte solution described above is prepared.

As shown in FIG. 2, the lithium battery 1 includes a positive electrode 3, a negative electrode 2, and a separator 4. The positive electrode 3, the negative electrode 2, and the separator 4 described above are wound or folded to be accommodated in the battery case 5. Subsequently, an organic electrolyte is injected into the battery case 5 and sealed with a cap assembly 6 to complete the lithium battery 1. The battery case may have a cylindrical shape, a square shape, or a thin film type. For example, the lithium battery may be a large thin film type battery. The lithium battery may be a lithium ion battery.

A separator may be disposed between the positive electrode and the negative electrode to form a battery structure. After the battery structure is stacked in a bi-cell structure, it is impregnated with an organic electrolyte, and the resulting product is accommodated in a pouch and sealed to complete a lithium ion polymer battery.

In addition, a plurality of the battery structures are stacked to form a battery pack, and the battery pack may be used in all devices requiring high capacity and high output. For example, it can be used for laptop computers, smart phones, electric vehicles, and the like.

In addition, since the lithium battery has excellent life characteristics and high rate characteristics, it can be used in an electric vehicle (EV). For example, it can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in a field requiring a large amount of power storage. For example, it can be used for electric bicycles, power tools, and the like.

Mode for carrying out the invention

The present invention will be described in more detail through the following examples and comparative examples. However, the examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

(Preparation of organic electrolyte)

Example 1: LDFOP (1%) + TCEB (1%)

In a 2:4:4 volume ratio mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), 1.15M LiPF ₆ was used as a lithium salt, and the following formula 8 was used based on the total weight of the organic electrolyte. 1% by weight of lithium difluoro bis-(oxalato)phosphate, LDFOP), which is a metal salt represented, and tris(2-cyanoethyl)borate represented by the following formula (16) (tris(2) -cyanoethyl) borate), tricyanoethyl borate, TCEB) 1% by weight was added to prepare an organic electrolyte.

<Formula 8> <Formula 16>

Example 2: LDFOP (1%) + TCEB (1%) + FEC (1%)

In a 2:4:4 volume ratio mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), 1.15M LiPF ₆ was used as a lithium salt, and the following formula 8 was used based on the total weight of the organic electrolyte. An organic electrolyte was prepared by adding 1% by weight of the metal salt represented, 1% by weight of tris(2-cyanoethyl) borate represented by the following formula (16), and 1% by weight of fluoroethylene carbonate represented by the following formula (14).

<Formula 8> <Formula 16> <Formula 14>

Example 3: LDFOP (1%) + TCEB (0.5%) + FEC (1%)

Except for adding 1% by weight of a metal salt represented by Formula 8, 0.5% by weight of tris(2-cyanoethyl) borate represented by Formula 16, and 1% by weight of fluoroethylene carbonate represented by Formula 14 An organic electrolyte was prepared in the same manner as in Example 2.

Example 4: LDFOP (1%) + TCEB (0.25%) + FEC (1%)

Except for adding 1% by weight of a metal salt represented by Formula 8, 0.25% by weight of tris(2-cyanoethyl) borate represented by Formula 16, and 1% by weight of fluoroethylene carbonate represented by Formula 14 An organic electrolyte was prepared in the same manner as in Example 2.

Example 5: LDFOP (1%) + TCEB (0.5%) + FEC (3%)

Except for adding 1% by weight of a metal salt represented by Formula 8, 0.5% by weight of tris(2-cyanoethyl) borate represented by Formula 16, and 3% by weight of fluoroethylene carbonate represented by Formula 14 An organic electrolyte was prepared in the same manner as in Example 2.

Example 6: LDFOP (1%) + TCEB (0.5%) + FEC (0.5%)

Except for adding 1% by weight of a metal salt represented by Formula 8, 0.5% by weight of tris(2-cyanoethyl) borate represented by Formula 16, and 0.5% by weight of fluoroethylene carbonate represented by Formula 14 An organic electrolyte was prepared in the same manner as in Example 2.

Example 7: LiFOB (1%) + TCEB (0.5%)

In a 2:4:4 volume ratio mixed solvent of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC), 1.15M LiPF ₆ was used as a lithium salt, and the following formula (10) was used based on the total weight of the organic electrolyte. An organic electrolyte was prepared by adding 1% by weight of the metal salt represented and 0.5% by weight of tris(2-cyanoethyl) borate (tricyanoethyl) borate represented by the following formula (16).

<Formula 10> <Formula 16>

Example 8: LiFOB (1%) + TCEB (0.5%) + FEC (3%)

In a 2:4:4 volume ratio mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), 1.15M LiPF ₆ was used as a lithium salt, and the following formula 8 was used based on the total weight of the organic electrolyte. An organic electrolyte was prepared by adding 1% by weight of the metal salt represented, 0.5% by weight of tris(2-cyanoethyl) borate represented by the following formula (16), and 3% by weight of fluoroethylene carbonate represented by the following formula (14).

<Formula 10> <Formula 16> <Formula 14>

Comparative Example 1: No additives

An organic electrolyte was prepared by adding 1.15M LiPF ₆ as a lithium salt to a 2:4:4 volume ratio mixed solvent of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC).

Comparative Example 2: LDFOP (1%) only

In a 2:4:4 volume ratio mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), 1.15M LiPF ₆ was used as a lithium salt, and the following formula 8 was used based on the total weight of the organic electrolyte. An organic electrolyte was prepared by adding 1% by weight of the indicated metal salt.

<Formula 8>

Comparative Example 3: TCEB (1%) only

In a 2:4:4 volume ratio mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), 1.15M LiPF ₆ was used as a lithium salt, and tris(2-) represented by the following formula (16) An organic electrolyte was prepared by adding 1% by weight of cyanoethyl) borate.

<Formula 16>

Comparative Example 4: FEC (1%) only

In a 2:4:4 volume ratio mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), 1.15M LiPF ₆ was used as a lithium salt, and the following formula 14 was used based on the total weight of the organic electrolyte. An organic electrolyte was prepared by adding 1% by weight of the indicated fluoroethylene carbonate.

<Formula 14>

Comparative Example 5: LDFOP (1%) + FEC (1%)

In a 2:4:4 volume ratio mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), 1.15M LiPF ₆ was used as a lithium salt, and the following formula 8 was used based on the total weight of the organic electrolyte. An organic electrolyte was prepared by adding 1% by weight of the metal salt represented and 1% by weight of fluoroethylene carbonate represented by the following formula (14).

<Formula 8> <Formula 14>

Comparative Example 6: TCEB (1%) + FEC (1%)

In a 2:4:4 volume ratio mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), 1.15M LiPF ₆ was used as a lithium salt, and the following formula (16) was used based on the total weight of the organic electrolyte. An organic electrolyte was prepared by adding 1% by weight of tris(2-cyanoethyl)borate and 1% by weight of fluoroethylene carbonate represented by the following formula (14).

<Formula 16> <Formula 14>

Comparative Example 7: LDFOP (1%) + VEC (0.5%)

In a 2:4:4 volume ratio mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), 1.15M LiPF ₆ was used as a lithium salt, and the following formula 8 was used based on the total weight of the organic electrolyte. An organic electrolyte was prepared by adding 1% by weight of the displayed metal salt and 0.5% by weight of vinyl ethylene carbonate (VEC).

<Formula 8>

(Manufacture of lithium battery)

Example 9

(Cathode manufacturing)

After mixing 97% by weight of graphite particles (MC20, Mitsubishi Chemical), 1.5% by weight of (Daicel's BM408) as a conductive material, and 1.5% by weight of (Zeon's BM400-B) as a binder, they are added to distilled water. Then, a negative active material slurry was prepared by stirring for 60 minutes using a mechanical stirrer. The slurry was applied to a thickness of about 60 μm on a copper current collector having a thickness of 10 μm using a doctor blade, dried for 0.5 hours in a hot air dryer at 100° C., dried again for 4 hours under vacuum and 120° C., and rolled (roll press) to prepare a negative electrode plate. The mixture density (E/D) of the negative electrode is 1.55 g/cc, and the loading level (L/L) is 14.36 mg/cm ² .

(Anode manufacturing)

Zr-coated LiNi ₆₅ Co ₂₀ Mn ₁₅ O ₂ (NCM 65, Samsung SDI) 94% by weight, as a conductive material (Denka black) 3.0% by weight and a binder (PVDF, Solef 6020 from Solvay) 3.0% by weight were mixed -After the methyl-2-pyrrolidone was added to the solvent, the mixture was stirred for 30 minutes using a mechanical stirrer to prepare a positive electrode active material slurry. The slurry was applied to a thickness of about 60 μm on an aluminum current collector having a thickness of 20 μm using a doctor blade, dried for 0.5 hours in a hot air dryer at 100° C., dried once again under vacuum and 120° C. for 4 hours, and rolled (roll press) to prepare a positive electrode plate. The mixture density (E/D) of the positive electrode is 3.15 g/cc, and the loading level (L/L) is 27.05 mg/cm ² .

(Battery assembly)

A pouch-shaped lithium battery was manufactured using the (ceramic coated 16 micron-thick polyethylene separator SK Innovation) and the organic electrolyte prepared in Example 1 as an electrolyte.

Examples 10 to 16

A lithium battery was manufactured in the same manner as in Example 9, except that the organic electrolyte prepared in Examples 2 to 8 was used instead of the organic electrolyte prepared in Example 1.

Comparative Examples 8 to 14

A lithium battery was manufactured in the same manner as in Example 9, except that the organic electrolyte prepared in Comparative Examples 1 to 7 was used instead of the organic electrolyte prepared in Example 1.

Evaluation Example 1: Viscosity Measurement

The viscosity was measured for the organic electrolytes prepared in Examples 1 to 8 and Comparative Examples 1 to 6, and some of the results are shown in Table 1 below.

The viscosity was measured using a viscometer SV-1A (A&D Company; Vibro ciscometer).

Viscosity [cp] Example 2 6.48 Comparative Example 1 5.96 Comparative Example 2 6.70 Comparative Example 3 7.14 Comparative Example 4 6.88 Comparative Example 5 7.45 Comparative Example 6 6.86

As shown in Table 1, the organic electrolyte of Example 2 had a significantly reduced viscosity compared to the organic electrolytes of Comparative Examples 1 to 6.

Evaluation Example 2: Room temperature (25°C) charge and discharge characteristics evaluation

The lithium batteries prepared in Examples 9 to 16 and Comparative Examples 8 to 14 were charged at a constant current at room temperature (25°C) at a current of 0.5C until the voltage reached 4.20V (vs. Li), followed by constant voltage charging. While maintaining 4.20V in the mode, cut-off was performed at a current of 0.05C rate. Subsequently, at the time of discharge, discharge was performed at a constant current of 0.5C rate until the voltage reached 2.80V (vs. Li) (formation step, 1 ^st cycle).

The lithium battery that has undergone the formation step is charged at a constant current at 25°C at a current of 0.5C until the voltage reaches 4.20V (vs. Li), and then cut off at a current of 0.05C rate while maintaining 4.20V in the constant voltage mode. (cut-off). Then, until the voltage at the time of discharge to 2.80V (vs. Li) was repeated cycles of discharging at a constant current of 1.5C rate to 200 ^th cycle.

Some of the results of the charge/discharge experiment are shown in Table 2 below. The capacity retention rate in the 200 ^th cycle is defined by Equation 1 below.

<Equation 1>

Capacity retention rate = [discharge capacity at 200 ^th cycle/1 discharge capacity at ^st cycle] × 100

Evaluation Example 3: High-temperature (45°C) charge and discharge characteristics evaluation

Charging and discharging were performed in the same manner as in Evaluation Example 2, except that the charging and discharging temperature was changed to 45°C.

Some of the results of the charge/discharge experiment are shown in Table 2 below.

Capacity retention rate at 25℃, 200 ^th cycle [%] Capacity maintenance rate at 45℃, 200 ^th cycle [%] Example 9 96.3 94.6 Example 10 96.3 94.6 Example 11 96.1 95.9 Example 12 95.8 95.2 Example 13 97.0 94.9 Example 14 96.2 95.8 Example 15 95.8 94.9 Example 16 98.1 96.4 Comparative Example 8 92.8 93.8 Comparative Example 9 93.6 94.7 Comparative Example 10 92.2 93.0 Comparative Example 11 93.9 94.0 Comparative Example 12 94.3 93.3 Comparative Example 13 93.5 95.1

As shown in Table 2 and FIGS. 1A to 1C, the lithium batteries of Examples 9 to 16 containing the organic electrolyte of the present invention are at room temperature compared to the lithium batteries of Comparative Examples 8 to 13 that do not contain the organic electrolyte of the present invention. (25°C) and high temperature (45°C) life characteristics are improved.

Evaluation Example 4: High temperature (45°C) DC resistance (DC IR) evaluation

Direct current resistance (CDIR) was measured by the following method.

The lithium batteries prepared in Examples 9 to 16 and Comparative Examples 8 to 14 were charged at a high temperature (45° C.) with a current of 0.5 C in the 1st cycle to a voltage of 50% SOC, and then cut off at 0.02 C. 10 After resting for a minute,

After constant rectification discharge at 0.5C for 30 seconds, rest for 30 seconds, charge at 0.5C for 30 seconds constant current and rest for 10 minutes,

After constant rectification discharge at 1.0C for 30 seconds, rest for 30 seconds, charge at 0.5C for 1 minute constant current, and rest for 10 minutes,

After constant rectification discharge at 2.0C for 30 seconds, rest for 30 seconds, charge at 0.5C for 2 minutes constant current and rest for 10 minutes,

After constant rectification discharge at 3.0C for 30 seconds, rest for 30 seconds, constant current charging at 0.5C for 2 minutes, and rest for 10 minutes.

The average voltage drop for 10 seconds for each C-rate is the DC voltage value.

A part of the measured DC resistance is shown in Table 3 below.

DC resistance increase rate at high temperature (45℃) [%] Example 9 132 Example 10 107 Example 11 109 Example 12 99 Example 13 94 Example 14 97 Example 15 110 Example 16 115 Comparative Example 8 148 Comparative Example 9 109 Comparative Example 10 179 Comparative Example 11 133 Comparative Example 12 127 Comparative Example 13 114

As shown in Table 3, the lithium batteries of Examples 9 to 16 containing the organic electrolyte of the present invention are at a higher temperature (45° C.) than the lithium batteries of Comparative Examples 8 to 13 that do not contain the organic electrolyte of the present invention. The rate of increase of the direct current resistance was significantly reduced.

therefore. It can be seen that generation of a high-resistance solid electrolyte film was suppressed in the lithium battery of the embodiment.

Evaluation Example 4: 60 ℃ high temperature stability test

Regarding the lithium batteries prepared in Examples 9 to 16 and Comparative Examples 8 to 13 at room temperature (25° C.), constant current charging up to 4.2 V at a rate of 0.5 C in the 1st cycle, and then maintaining at 4.20 V, A constant voltage was charged until the current reached 0.05C, and a constant current was discharged to 2.75V at a rate of 0.5C.

2 ^nd cycle was constant-voltage charge until the current is a constant current charging until 0.05C and 4.20V at a rate of 0.5C, and then maintained at a constant current discharge was 4.20V to 2.80 V at a rate of 0.2C.

3 ^rd cycle was kept at the constant current charging and then at a rate of 0.5C to 4.20V 4.20V constant voltage charge until the current to be the constant current discharge until 0.05C was 2.80 V at a rate of 0.2C. The discharge capacity at the 3 ^rd cycle was regarded as a standard capacity.

Charged to 4.20 V at a rate of 0.5C in the 4th cycle, and then charged at a constant voltage until the current becomes 0.05C while maintaining at 4.20 V, and then the charged battery in an oven at 60° C. for 10 days, 30 days, and 60 days After storage, the battery was taken out and discharged for 4th cycle to 2.75 V at a rate of 0.1 C. Some of the charging and discharging results are shown in Table 4 below. The capacity retention rate after high temperature storage is defined by Equation 2 below.

<Equation 2>

Capacity retention rate after high temperature storage[%]= [Discharge capacity after high temperature storage in 4th cycle / standard capacity] × 100

(The standard capacity is the discharge capacity at the 3 ^rd cycle)

Capacity retention rate after storage for 60 days [%] Example 9 86.78 Example 10 86.28 Example 11 86.74 Example 12 87.09 Example 13 86.27 Example 14 88.08 Example 15 88.46 Example 16 89.72 Comparative Example 8 83.22 Comparative Example 9 84.59 Comparative Example 10 83.43 Comparative Example 11 85.20 Comparative Example 12 85.60 Comparative Example 13 85.98

As shown in Table 4, the lithium batteries of Examples 9 to 16 containing the organic electrolyte of the present invention significantly increased high temperature stability compared to the lithium batteries of Comparative Examples 8 to 13 that do not contain the organic electrolyte of the present invention. .

Evaluation Example 5: Gas generation amount experiment

For the lithium batteries prepared in Examples 9 to 16 and Comparative Examples 8 to 14, the amount of gas generated in the process of evaluating the life characteristics at high temperature (45° C.) was measured, and some of the results are shown in Table 5 below. After popping the finished cell into a jig, the change in internal gas pressure was converted into a volume to measure the amount of gas produced.

Gas generation amount [ml] Example 13 0.79 Comparative Example 14 2.12

As shown in Table 5 above, the lithium battery of Example 13 containing the organic electrolyte of the present invention significantly reduced the amount of gas generated compared to the lithium battery of Comparative Example 14 not containing the organic electrolyte of the present invention.

By using an organic electrolyte of a new composition, the life characteristics of a lithium battery can be improved.

Claims (20)

Organic solvent;
Lithium salt;
A borate compound represented by the following formula (1);
An ionic metal complex represented by the following formula (2); And
It includes a fluorine-based compound represented by the following Chemical Formula 13
The content of the borate compound is 0.1 to 10% by weight based on the total weight of the organic electrolyte,
The content of the ionic metal complex is 0.1 to 10% by weight based on the total weight of the organic electrolyte,
An organic electrolyte in which the content of the fluorine-based compound is 0.1 to 10% by weight based on the total weight of the organic electrolyte:
<Formula 1><Formula2><Formula2>

In Formulas 1, 2, and 13,
R ₁ , R ₂ and R ₃ are each independently hydrogen; A halogen substituted or unsubstituted C1 to C5 alkyl group; Or a halogen substituted or unsubstituted C 1 to C 5 cyanoalkyl group; And,
At least one of R ₁ , R ₂ and R ₃ includes a cyanoalkyl group,
Me is an element selected from the group consisting of transition metals and elements belonging to groups 13 to 15 of the periodic table,
M is a metal ion,
a is an integer of 1 to 3, b is an integer of 1 to 3, s=b/a,
p is 0 to 8, q is 0 or 1, r is 1 to 4,
X ₁ and X ₂ are each independently O, S, or NR ₆ ,
R ₄ and R ₆ are halogen, a halogen substituted or unsubstituted C 1 to C 5 alkyl group, or a halogen substituted or unsubstituted C 1 to C 5 aryl group,
R ₅ is an alkylene group having 1 to 5 carbon atoms substituted or unsubstituted with halogen, an arylene group having 4 to 10 carbon atoms substituted or unsubstituted with halogen,
In Chemical Formula 13,
X ₁ and X ₂ are each independently hydrogen; halogen; It is an alkyl group unsubstituted or substituted with a halogen having 1 to 2 carbon atoms, and at least one of X ₁ and X ₂ contains a fluorine atom. The organic electrolyte according to claim 1, wherein the borate compound is represented by the following formula (3):
<Formula 3>
B(OR ₁₀ ) ₃
In the above formula,
R ₁₀ is halogen-substituted or unsubstituted C 1 to C 5 cyanoalkyl. The organic electrolyte according to claim 1, wherein the borate compound is tricyanomethylborate, tricyanoethylborate, tricyanopropylborate or tricyanobutylborate. The organic electrolyte of claim 1, wherein the ionic metal complex compound is represented by the following formula (4):
<Formula 4>

In the above formula,
Ma is Al, B or P,
M is a metal ion,
p is 0 to 8, q is 0 or 1, r is 1 to 4,
X ₃ and X ₄ are each independently O or S,
R ₇ is halogen,
R ₈ is each independently a halogen-substituted or unsubstituted C 1 to C 5 alkylene group, or a halogen-substituted or unsubstituted C 4 to C 10 arylene group. The organic electrolyte according to claim 1, wherein the ionic metal complex compound is represented by the following formula (5) or (6):
<Formula 5><Formula6>

In the above equations,
Ma is Al, B or P,
p is 0 to 8, r is 1 to 4,
R ₇ is halogen,
R ₉ is a halogen-substituted or unsubstituted C 1 to C 5 alkylene group. The organic electrolyte according to claim 1, wherein the ionic metal complex compound is represented by the following formulas 7 to 12:
<Formula 7><Formula8>

<Formula 9><Formula10>

<Formula 11><Formula12>

. delete delete delete The organic electrolyte of claim 1, wherein the fluorine-based compound is represented by the following formulas 14 to 15:
<Formula 14><Formula15>

. delete The organic electrolyte according to claim 1, wherein the organic solvent contains a low boiling point solvent. The method of claim 1, wherein the organic solvent is at least one selected from the group consisting of dialkyl carbonates, cyclic carbonates, linear or cyclic esters, linear or cyclic amides, aliphatic nitriles, linear or cyclic ethers, and derivatives thereof. Organic electrolyte. The method of claim 1, wherein the organic solvent is dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, diethyl carbonate (DEC), dipropyl carbonate, propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate, ethyl propionate, ethyl butyrate, acetonitrile, succinonitrile (SN), dimethyl sulfoxide, dimethylformamide, dimethyl acetamide, gamma-valerolactone, gamma-butyrolactone and An organic electrolytic solution comprising at least one selected from the group consisting of tetrahydrofuran. The method of claim 1, wherein the lithium salt in the organic electrolyte is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ ) (C _y F _2y+1 SO ₂ ) (x, y are 1 to 20), LiCl and LiI containing at least one selected from the group consisting of Organic electrolyte. The organic electrolyte according to claim 1, wherein the lithium salt is LiPF ₆ in the organic electrolyte. The organic electrolyte according to claim 1, wherein the concentration of the lithium salt in the organic electrolyte is 0.01 to 2.0 M. anode;
cathode; And
A lithium battery comprising the organic electrolyte according to any one of claims 1 to 6, 10, and 12 to 17. The lithium battery according to claim 18, wherein the positive electrode contains nickel. The lithium battery according to claim 18, wherein the negative electrode comprises graphite.

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